The present disclosure relates generally to the etching of polysilicon, and more particularly to plasma-based etching of polysilicon with a high selectivity.
Plasma-based etching can be an important processing step in the fabrication of integrated circuits. Typically, removal of polysilicon can be performed using wet or dry reactive-ion-etch (RIE) processes.
A wet etching process can result in a low etch rate of polysilicon, which leads to a low throughput. Furthermore, a wet etching process may not achieve as high of selectivity over other materials as dry etching processes.
A dry RIE process can result in greater cost due at least in part to complicated hardware for controlling ion direction and energy using an external bias. In addition, the use of a dry RIE process can damage surrounding structures due to exposure to ion and photon fluxes. The surrounding structures can be sidewalls made of, for example, exposed nitrides and/or oxides. Such surrounding structures can include silicon nitride (Si3N4), titanium nitride (TiN), and silicon oxide (SiO2) including thermal oxide.